Highly crimped polynosic fibers

ABSTRACT

A VISCOE HAVING A Y-VALUE OF AT LEAST 50 IS EXTENDED INTO A COAGULATION BATH CONTAINING FORMALDEHYDE, AND THE RESULTING FILAMENTS ARE STRETCHED IN A SECOND BATH AT 45* TO 75*C. UNDER A TENSION OF UP TO 0.3 G./D, AND THEN TREATED IN A THIRD BATH CONTAINING ALKALI METAL, ALKALINE EARTH METAL AND/OR AMMONIUM SALTS OF SUFURIC ACID AT THE PH OF 2.0 TO 10.5 AND A TEMPERATURE OF 30* TO 70* C. THE OBTAINED HIGHLY CRIMPED POLYNOSIC FIBERS HAVE AN ASYMMETRIC STRUCTURE WITH A CORE-STAINABLE LAYER POSITIONED AT THE INSIDE TRACK OF THE CRIMP BEND, THE DYE EXHAUSTION IS AT LEAST 40%, WET MODULUS IS 0.5 TO 1.8 G./D. AND CRIMPS ARE MORE THAN 10/25 MM.

June 26, 1973 MAsMCHl KUBOTA ETAL 3,741,862

HIGHLY CRIMPED PoLYNosIC FIBERS Original Filed Sept. 22, 1967 2Sheets-Sheet l @manner/mw) Q Q 3 /VUZSQI (S7/0 June 26, 1973 MASA|CH|KUBQTA EVAL 3,741,862

HIGHLY CRIMPED POLYNOSIC FIBERS Original Filed Sept. 22, 1967 2Shee'cs--Shee'fl Z United States Patent O 3,741,862 HIGHLY CRIMPEDPOLYNOSIC FIBERS Masaicho Kubota, Taro Yamamura, Atsushi Kawai, and

Takehiro Katsuyama, Ohtake, Masamich Ikeda, Iwakuni, and Seiichi moto,Ohtake, Japan, assignors to Mitsubishi Rayon Co., Ltd., Tokyo, JapanOriginal application Sept. 22, 1967, Ser. No. 669,800, now Patent No.3,574,812. Divided and this application Aug. 27, 1970, Ser. No. 67,591

Claims priority, application Japan, Sept. 22, 1966, 41/ 62,595; Oct. 12,1966, 41/ 67,012 Int. Cl. D01d 5/22; D01f 3/28; D02g 3/00 U.S. Cl.161-173 2 Claims ABSTRACT 0F THE DISCLOSURE A viscose having a y-valueof at least 50 is extended into a coagulation bath containingformaldehyde, and the resulting filaments are stretched in a second bathat 45 to 75 C. under a tension of up to 0.3 g./d. and then treated in athird bath containing alkali metal, alkaline earth metal and/or ammoniumsalts of sulfuric acid at a pH of 2.0 to 10.5 and a temperature of 30 to70 C. The obtained highly crimped polynosic fibers have an asymmetricstructure with a core-stainable layer positioned at the inside track ofthe crimp bend; the dye exhaustion is at least 40%, wet modulus is 0.5to 1.8 g./ d. and crimps are more than /25 mm.

This application is a division of application for U.S. Letters PatentSer. No. 669,800, filed Sept. 22, 1967, now Pat. No. 3,574,812.

The present invention relates to improved highly crimped polynosicfibers and a process for producing the same.

Recently, there have been proposed many processes for producingpolynosic fibers having excellent properties by extruding a viscosehaving high 'y-value into a coagulation bath containing formaldehyde andstretching the resulting filaments in a hot dilute acid bath (secondbath).

The filaments which have been withdrawn from the coagulation bathcontaining formaldehyde have high stretchability, and therefore whenthey are highly stretched in the second bath kept at a relatively hightemperature, there are obtained fibers having high tenacity, high wetmodulus and high resistance to water and alkali solutions.

The above-mentioned processes are disclosed in, for example, U.S. Pats.Nos. 2,937,070, 3,107,970 and 3,226,- 461, British Pats. Nos. 910,878,993,786 and 1,027,153, French Pats. Nos. 1,266,492, 80,3l4/1,266,49'2,1,302,294 and 1,351,736, and Belgian Pats. Nos. 602,660, 608,811 and626,075.

On the other hand, when the filaments formed in the coagulation bathcontaining formaldehyde are stretched in the second bath at a relativelylow temperature and under such a small tension as 0.3 g./d. or less andare then relaxed in a third aqueous bath, crimped polynosic fibers canbe obtained.

Generally, fibers obtained by use of a coagulation bath containingformaldehyde have many such excellent characteristics as mentionedabove. On the other hand, however, they are not sufficient in elongationand dyeability and are not satisfactory in knot tenacity and the like.

It has been found that in order to establish a method for improvingfiber properties, it is extremely effective to adopt a process in whichthe filaments, obtained by extruding a viscose having a y-value of atleast 50 into a coagulation bath containing sulfuric acid, sodiumsulfate and formaldehyde and then stretching the resulting filaments ina second bath kept at 45 to 75 C. under a tensionV of up to 0.3 g./d.,are treated with an aqueous 3,741,862 Patented June 26, 1973 "icesolution (third bath) containing an alkali metal salt of sulfuric acid,alkaline earth metal salt of sulfuric acid, ammonium salt of sulfuricacid or a mixture thereof, said third aqueous bath being kept at a pH of2.0 to 10.5 and at a temperature of 30 to 70 C. The third bath may alsocontain a small amount of a sulfuric acid salt of zinc or cadmium.

When the filaments, which have been prepared by extruding a highfy-value viscose into a coagulation bath containing sulfuric acid,sodium sulfate and formaldehyde and then stretching the resultingfilaments in a second bath, are introduced into an aqueous solution of,for example, sodium sulfate, the filaments unexpectedly swell to a greatextent and they are sometimes dissolved after a period of time. Such aphenomenon is observed not only in the case of sodium sulfate but alsoin the case of sulfurie acid salts of other alkali metals, alkalineearth metals or ammonia. Such swelling action is greatly affected by thepH and temperatures of the salt solutions employed. Therefore the pH andtemperatures of the salt solutions to be used in the present inventionshould be within the ranges as described above. If the pH is less than2.0, the diffusion of hydrogen ion into the fiber becomes marked,whereby the effective swelling of fiber due to the salt employed isrestrained. On the other hand, if the pH is more than 10.5, the fiber isswelled to a great extent and is markedly lowered in tenacity. Moreover,even when, in the above case, a sulfuric acid salt of zinc or cadmium isincorporated into the salt solution, the specific action describedhereinafter cannot be displayed. As to the temperature, it may be saidthat the higher the temperature, the stronger the swelling action of thesalt. However, if the temperature is excessively high, regeneration ofthe fiber progresses to make difficult the swelling of the fiber. Thepreferred treatment temperature is within the range of 30 to 70 C. Ithas also been found that when an aqueous solution of a salt having aswelling action on fiber, as mentioned above, is incorporated with sucha slight amount as less than 0.5 g./l. of a sulfuric acid salt of zincor cadmium, the swelling of the fiber is suitably controlled and thefiber properties are improved more effectively.

In practicing the present process on a commercial scale, there isordin-arily used as a third bath an aqueous solution containing up to 50g./l. of sodium sulfate and up to l g./l. of sulfuric acid. The thirdbath, however, desirably contains, additionally, up to 0.5 g./l. of zincsulfate.

In the present invention, only fibers which are produced using acoagulation bath containing formaldehyde can be treated with an aqueoussalt solution and the stretched filaments are still high in fy-value.From the above, it is concluded that the swelling or dissolution of thefibers by action of said salts is ascribable to behavior peculiar tocellulose hydroxymethyl-xanthate, which is a reaction product ofcellulose xanthate and formaldehyde.

In the accompanying drawings, FIG. 1 is a graph which expresses theabove general relationship, and FIG. 2 shows the cross section of thefibers obtained by treatment in accordance with the present invention.

FIGS. 3 and 4 show the side view of the present ber and a conventionalfiber.

In FIG. 1, the horizontal axis is graduated to show the sodium sulfateconcentration in the third bath, while the vertical axis shows the dyeexhaustion as a characteristic representing the swelling effect. Thesolid line shows the case where a viscose containing 7% of cellulose andv4% of alkali and having a 'y-value of 80 and a viscosity of 260 poisesis extruded into a coagulation bath containing 26 g./1. of sulfuricacid, 75 g./l. of sodium sulfate,

v0.1 g./l. of zinc sulfate and 7.5 g./l. of formaldehyde and kept at 25C., and the resulting filaments are stretched to 380% in a second bathkept at 70 C. and are then treated in a third aqueous bath containing upto g./l. of sodium sulfate and 0.1 g./l. of zinc sulfate and kept at 70C. The dotted line shows the case where the ltreatments are effectedunder the same conditions as above except that no formaldehyde iscontained in the coagulation bath and the stretch ratio in the secondbath is 150%. From this graph, it is clear that no swelling effect isdisplayed at all when the coagulation bath contains no formaldehyde.Conditions for measuring the dye exhaustion are as follows:

Sample: 3 g.

Iapanol Brilliant Blue `6BKX: 0.3% (o.w.f.) Sodium sulfate: (o.w.f.)

Bath ratio: 1:100`

Temperature and time: 45 C. X20 minutes The absorbance of the residualliquid is measured by means of a photoelectric colorimeter to calculatethe dye exhaustion.

In FIG. 2, black parts show the skin-stained layer. For skin-staining,fibers are stained using the following conditions followed by washingthrough the alcohol series.

Iapanol Brilliant Blue 6BKX (C.I. Direct Blue 1): 1%

(o.w.f.)

Sodium chloride: 10% (o.w.f.)

Temperature and time: 100 C. 30 minutes In FIGS. 3 and 4, black partsshow the core-stained layer. For core-staining, fibers are stained usingthe following conditions, followed by washing with water anddehydration.

Solophenyl Fast Blue Green B.L. (C.I. Direct Green 27):

1% (o.w.f.)

Sodium sulfate: 0.3% (o.w.f.)

Temperature yand time: Ambient temperature 5 hours When the treatingmethod of the present invention is applied to filaments which have beenstretched in the second bath under a tension of less than 0.3 g./d., theresulting fibers are more improved, without any substantial lowering intenacity, in lateral properties of fiber, such as elongation, knottenacity and abrasion resistance, and in dyeability as well as in degreeof crimp.

The present process will be explained in more detail below.

The y-value of the viscose employed is required to be at least 50,preferably at least 65 (corresponding to a salt point of at least 16).If the ly-value is lower than said value, the effect of formaldehyde inthe coagulation bath is not suicient and no satisfactory crimps can bedeveloped.

The formaldehyde concentration of the coagulation bath is preferably 4to 15 g./1. It is particularly desirable that the sulfuric acidconcentration of the coagulation bath is within the range defined by thefollowing equations:

Minimum concentration of sulfuric acid (g./l.) =3A+8 Maximumconcentration of sulfuric acid (g./1.)=8A}-16 wherein A is the totalalkali concentration in viscose which is preferably 2 to 8%. Theconcentration of sodium sulfate is preferably 20 to 250 g./l., and thatof zinc sulfate, if it is to be incorporated, is desirably up to 0.3g./l.

The filaments withdrawn from the coagulation bath are then stretched inthe second bath. In this case, the temperature of the bath and thetension applied to the filaments during stretching are the mostimportant factors. The temperature of the second bath is within therange of 45 to 75 C. If the bath temperature is out of said range, noexcellent crimps can be developed. The tension applied to the filamentsduring stretching should be less than 0.3 g./d. If the tension is morethan 0.3 g./d., no highly crimped fibers can be obtained. The secondbath preferably contains a small amount of sulfuric acid,.in

view of the subsequent treatment. The bath may also contain smallamounts of salts and formaldehyde.

The filaments, which have been stretched in the above manner, are thenrelaxed, either as such or after cutting to staples, in a third bathcomprising an aqueous salt solution, whereby the fibers undergo swellingaction and, at the same time, develop markedly fine crimps. In thiscase, the temperature of the third bath is 30 to 70 C. If thetemperature is below 30 C., the swelling effect is low, while if thetemperature is above 70 C., no excellent crimps are developed. Thefibers which have developed crimps are then transferred to a hightemperature acidic bath to complete regeneration.

The fibers obtained according to the above-rnentioned process have suchcharacteristics as described below.

The cross section and side view of the fiber are in such a specific formas shown in FIGS. 2 and 3, respectively, and in the fibers, thecore-stainable layer is biassed. Thus, the fibers have a heterogeneousstructure as if they were conjugate fibers. The crimp of the fibers isin a spiral form but, unlike the case of a conventional crimped lstaplefiber as shown in FIG. 4, the core-stainable layer is always positionedat the inside track of the crimp bend. In water, therefore, the crimp isstraightened to a certain extent due to greater swelling of thecore-stainable layer, but is completely restored on drying. That is, thefiber of the present invention has such a property as that of woolhaving so-called water reversible crimps. In contrast thereto, in thecase of the conventional conjugate fibers or the so-called brokenskin-type viscose crimped staples, the skin-stainable layer is alwayspositioned at the inside track of the crimp bend. Further, in the caseof the conventional crimped viscose staples also, the thicker side ofthe skin-stainable layer is positioned at the inside track of the crimpbend. These fibers, therefore, are different in behavior to water fromthe fibers of the present invention. It is considered that the excellentcrimp properties of the present fibers are derived from the aforesaidspecific structure, which is entirely different from that of theconventional crimped viscose staples.

The fibers of the present invention are not only excellent in crimpproperties but also have excellent mechanical properties. Tenacity andwet modulus of the fibers are far higher than those of the conventionalcommon crimped viscose staples. Particularly, the wet modulus at 5%elongation of the present fibers is, in general, 0.5 to 1.8 g./d. ormore. Therefore, the fibers are excellent in dimensional stability andcan withstand repeated washing. They are also high in knot tenacity andexcellent in abrasion resistance. The water retention of the fibers isequal to or somewhat higher than that of the recent polynosic fibers butthe water resistance and dimensional stability thereof are suicientlyhigh. Excellence in dyeability is also a great characteristic of thefibers. Concretely, the fibers have a dye exhaustion of more than 40%,ordinarily in the range of 45 to 85%, a wet tenacity of 1.*8 to 4 g./d.,a wet modulus at 5% elongation of 0.5 to 1.8 g./d., and crimps of morethan 10/25 mm.

Owing to those superior crimp and mechanical properties, the fibers canbe used in a wide variety of fabrics with or without synthetic or cottonfibers. lFabrics converted from the fibers have comfortable hand, highslipresistance, high dimensional stability and superior mechanicalproperties.

The following examples illustrate the present invention:

EXAMPLE 1 A viscous containing `6.5% of cellulose and 4.5% of totalalkali and having a viscosity of poises, a salt point of 21 and aly-value of 82 was extruded into a coagulation bath containing 35 g./l.of sulfuric acid, 75 g./l. of sodium sulfate and 7 g./l. of formaldehydeand kept `at 25 C. The filaments withdrawn from the coagulation bathwere immediately stretched to 300% the original length of the filamentsunder a tension of 0.05 g./d. in a second bath kept at 60 C. andcontaining 2 g./l. of sulfuric acid. Thereafter, the filaments wererelaxed in a third bath containing 5 g./l. of sodium sulpH of 3.4 todevelop crimps. Subsequently, the regeneration of the filaments werecompleted in an aqueous bath containing 5 g./l. of sulfuric acid andkept at 85 C. The ly-values of the filaments just before entering thesecond and third baths were 66 and 59, respectively. 'Fiber prop- 5 fateand 0.1 g./1. of Zinc sulfate and kept at 50 C. and erties of the thusobtalned fibers are shown 1n Table at a pH of 6.8 to develop crimps. The'y-values of the 2(A). filaments just before entering the second andthird baths For reference, fibers (B) were produced in the same were 65and 57, respectively. Subsequently, the regeneramanner as above, exceptthat the third bath employed tion of the @filaments were completed in anaqueous bath 10 contained only 10 g./l. of sulfuric acid and kept at apH containing 5 g./l. of sulfuric acid and kept at 85 C. of 1.4. Fiberproperties of this fibers are shown in Table and were then scouredaccording to a conventional pro- 2-(B).

TABLE 2 Wet Condimodulus Wet tioned at 5% Number Degree Wet elongaknotelongaof crimps of Dye Denier tenacity tion tenacity tion per crimpexhaustion (d) (gJd.) (percent) (g./d.) (g./d.) 25 mm. (percent)(percent) A 5.6 2.7 1.7 1.1 24 29 61 B 5.1 2.9 12 1.3 1 a 9 14 aocedure. Fiber properties of the thus obtained fibers are shown in Tablel-(A), and the cross section of the fiber after dyeing are shown in FIG.2.

For reference, fibers (B) were produced in the same manner as abo-ve,except that the third bath contained no sulfates and was kept at 50 C.Fiber properties of these fibers are as shown in Table l-(B).

What is claimed is:

1. An improved highly crimped polynosic fiber comprising a heterogeneousstructure asymmetric in the cross-sectional direction of the fiber,wherein a core-stainable layer is always positioned at the inside trackof the crimp bend, said fiber having a dye exhaustion of at least 2. Afiber according to claim 1, wherein the fiber has a TABLE 1 Wet Qondi-Condimodulus Number Conditioned Wet tioned at 5% of Degree tioned Wetelongaelonga.- knot e1ongacrimps of Dye Denier tenacity tenacity tiontion tenacity tion (per crimp exhaustion (d) (g./d.) g./d.) (percent(percent) (g./d.) (g./d.) 25 mm.) (percent) (bercent) EXAMPLE 2 wettenacity of 1.8 t0 4 g./ d., a Wet modulus at 5% elon- A viscosecontaining 7% of cellulose and 4.5% of alkali and having a viscosity of320 poises, a salt point of 22 and a ry-value of 84 was extruded into acoagulation bath containing 37 g./l. of sulfuric acid, 8O g./l. ofsodium sulfate and 8 g./l. of formaldehyde and kept at 23 C. Thefilaments Withdrawn from the coagulation bath were immediately stretchedto 290% the original length olf the filaments under a tension of 0.045g./d. in a second bath containing 1 g./l. of sulfuric acid and kept at60 C. Thereafter, the filaments were relaxed in a third bath containing0.2 g./l. sulfuric acid, 10 g./l. of sodium sulfate and 0.1 g./l. ofzinc sulfate, and kept at 50 C. at a gation of 0.5 to 1.8 g./d. andcrimps of more than References Cited UNITED STATES PATENTS 3,419,65212/1968 Kubota et al 264-168 GEORGE F. LEsMEs, Primary Examiner L. T.KENDELL, Assistant Examiner U.S. Cl. X.R.

